Hi,
Thanks for using our plugins. I can try to help out here, but I am limited in providing support on customizations.
It is possible that you could modify the template following our themer’s guide, but it would take knowledge in php, css, and html to do it:
https://theeventscalendar.com/knowledgebase/themers-guide/
There you could detect if an event is in a certain Event Category and change the title.
Another option that does not involve coding is to just create events for each one and call it Private Event.
I can try to answer some more questions about this, but limited in much more then this.
Let me know.
Thanks